Fair Value of Assets and Liabilities - Change In Unrealized Gains and Losses included in Net Income for Level 3 (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Gains (losses) included in net income for Level 3 assets and liabilities:
Total recurring Level 3 assets	$ 2	$ 1
Total recurring Level 3 liabilities	(25)	23
Contractholder funds: Derivatives embedded in life and annuity contracts
Gains (losses) included in net income for Level 3 assets and liabilities:
Total recurring Level 3 liabilities	(25)	23
Equity securities
Gains (losses) included in net income for Level 3 assets and liabilities:
Total recurring Level 3 assets	$ 2	$ 1